In the mechanical arts it is fairly common to find devices with a pair of nested members that reciprocate in ordinary use. For example, in the automotive industry, shock absorbers reciprocate and dampen transmitted shocks, and in the bicycle industry, forks are sometimes fitted with shock absorbers on certain types of bikes. In general, these shock absorbers have an outer cylindrical tube within which an inner tube is nested. The outer tube is usually stationary, and the inner tube reciprocates in the outer tube.
Recently, there have been several advances in the shock absorber area, especially as applied to vehicles. For example, the development of electro-rheological fluid-filled shock absorbers. These fluids are liquids filled with magnetic particles that line up in an applied magnetic field so that the liquid transforms instantaneously to a gel. The degree of gelling depends upon applied magnetic field strength, and that in turn depends upon the strength of the applied current to the electro-magnet generating the field. The change of form from a liquid to a gel permits better absorption of shocks and dampens out perturbations such as those encountered when the vehicle is driven on ordinary roads with common irregularities. These shock absorbers may also assist in high speed maneuvers by minimizing vehicular body sway. The extent to which an electro-rheological fluid gels depends upon the current applied, and the amount of current applied depends on the extent to which the shock absorber is reciprocated or displaced from a rest position. Thus, typically the farther the reciprocating action displaces the shock absorbers, the higher the applied current to counter the displacement forces, and the more resistant the gel becomes to counteract the forces. Since applying current is dependent upon displacement of the shock absorber inner tube from a rest position, it may be necessary or desirable for these systems for a controller of magnetic field strength to know the position of the inner tube relative to the outer tube instantaneously.
Accordingly, it is desirable to develop a system that determines in real time the position of reciprocating members relative to each other to facilitate improvements in a variety of mechanical systems. It is further desirable that the system generate a control signal for appropriate action. In addition, it is desirable that the system be robust and easily fitted to reciprocating members without otherwise interfering with operation of the members. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.